I'm going to avoid the cultural flamewar around whether companies should do this.
I don't mind it. I've interviewed for enough jobs and had enough acceptances and rejections to learn something: it's not a big deal. If you don't know an API function, you don't know it. The likelihood that you won't get the job because you didn't know that one question is unlikely.
In fact, part of the evaluation is whether you can handle not knowing the answer with grace. The fail-outs are the ones who use their cool or seem to think the question is stupid, not the ones who get it wrong.
Once you realize that you don't need to get all of the answers to pass an interview, it gets easier.
I don't mind it. I've interviewed for enough jobs and had enough acceptances and rejections to learn something: it's not a big deal. If you don't know an API function, you don't know it. The likelihood that you won't get the job because you didn't know that one question is unlikely.
In fact, part of the evaluation is whether you can handle not knowing the answer with grace. The fail-outs are the ones who use their cool or seem to think the question is stupid, not the ones who get it wrong.
Once you realize that you don't need to get all of the answers to pass an interview, it gets easier.